Tickborne Diseases -- Georgia, 1989

The Office of Epidemiology, Georgia Department of Human
Resources (GDHR), maintains surveillance for three tickborne
diseases--Lyme disease (LD), Rocky Mountain spotted fever (RMSF),
and human ehrlichiosis. This report summarizes data on the
occurrence of these three diseases in Georgia during 1989.
Lyme Disease

During 1989, 715 LD cases* were reported to the GDHR--a greater
than 12-fold increase from the 59 cases reported in 1988. Cases
peaked during the summer, when ticks are most active (Figure 1).
Onset for at least 84 (12%) patients occurred during previous
years. Each of the 19 health districts in Georgia reported one or
more cases of LD.

Of the 715 patients, 365 (51%) were female; 596 (84%) were
white, 36 (5%) were black, and 82 (11%) were of unrecorded race.
Median age of patients was 40 years (range: 1-85 years). Cases
were reported from 114 (72%) of the 159 counties in Georgia. A
band of counties across the midsection of Georgia accounted for
most of the cases and for the highest rates (Figure 2). This area
of the state also has the highest density of white-tailed deer,
which appear to play a major role in maintaining the life cycle
of Ixodes scapularis, the vector of LD in Georgia.
Rocky Mountain Spotted Fever

During 1989, 23 RMSF cases (0.4 cases per 100,000 population)
were reported to the GDHR. Six (26%) patients were less than 10
years of age, and 10 (43%) were less than 20 years of age (range:
4-71 years; median: 33 years). Seventeen patients (74%) were
male; all were white. Ten (43%) were hospitalized, and RMSF was
laboratory confirmed for 20 (87%). For 15 (65%) patients, a
history of tick attachment or exposure to a tick-infested area
was reported. Fever and/or headache were present in 20 (87%) of
patients, and rash, in 13 (57%). Three counties reported multiple
cases: Clarke (four cases), Cobb (three), and DeKalb (two).
Onsets of illness ranged from March 31 to November 17.
Ehrlichiosis

During 1989, one case of human ehrlichiosis was reported in
Georgia. A 25-year-old man from Richmond County had onset
November 7 and was hospitalized for a fever of unclear etiology.
Serologic tests confirmed the diagnosis of ehrlichiosis.
Reported by: T McKinley, MPH, D Smith, Office of Epidemiology, RK
Sikes, DVM, State Epidemiologist, Georgia Dept of Human
Resources. Div of Vector-Borne Infectious Diseases, Center for
Infectious Diseases, CDC.

Editorial Note

Editorial Note: LD is the most commonly reported vectorborne
disease in the United States (1). The approximately 7400 cases
provisionally reported for 1989 represent a 62% increase over
those reported for 1988 (2) and a 15-fold increase from 1982,
when national surveillance was established. As a result of
surveillance efforts, the epidemiology of LD, RMSF, and
ehrlichiosis is now more clearly defined, and preventive measures
have been identified (1-3). These measures include avoidance of
sites suspected to be infested with ticks; use of repellents and
acaracides, wearing of protective clothing, and frequent
inspection for and prompt removal of attached ticks.

The 12-fold increase in the number of LD cases reported by the
GDHR from 1988 to 1989 is one of the largest reported by any
state for a similar period; the Georgia rate in 1989 is among the
10 highest in the United States and is 10- to 20-fold greater
than the rates reported in surrounding states.
Laboratory-confirmed LD has consistently been concentrated
geographically in the northeastern, mid-Atlantic, north central,
and northern Pacific coastal areas (1,2). The high rate in
Georgia in 1989 may reflect a fundamental change in the local
epidemiology of the disease, an alteration in reporting resulting
from a major change in physician and public awareness, and/or a
change in availability or sensitivity of diagnostic tests.

During 1988 and 1989, the GDHR conducted extensive education
programs for both physicians and the public about LD and made
laboratory testing available. During this period, the GDHR public
health laboratory was the only laboratory in the state doing
serologic testing for LD. These factors also may have contributed
to increased reporting.

The diagnosis of LD may be difficult to make in some cases and
requires a careful assessment of clinical, epidemiologic, and
laboratory features. Signs and symptoms are often nonspecific,
and a history of tick exposure may be absent. Laboratory
diagnosis is problematic and cannot be relied on as the sole
determinant in evaluation of an individual case (4). Borrelia
burgdorferi is difficult to isolate by culture, even when present
in a clinical specimen. Serologic tests, especially in the early
phase of illness, are inadequately sensitive. In addition, these
tests are nonspecific, and crossreactions with other closely
related spirochetes can occur; some positive antibody reactions
in both humans and nonhuman hosts may be due to that
crossreactivity. Monoclonal antibodies are now being used to
identify B. burgdorferi in ticks (5); however, these tests are
difficult to perform and must be carefully interpreted.

migrans (EM) lesion and a history of tick exposure within 30 days
of onset or, in the absence of known tick exposure, an EM lesion
and a positive serologic test (immunofluorescence antibody (IFA)
titer greater than or equal to 128) or involvement of at least
one body system (musculoskeletal, cardiovascular, or nervous); or

in the absence of EM, a positive serologic test (IFA greater
than or equal to 128) and involvement of one or more body systems
(musculoskeletal, cardiovascular, or nervous).

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